In a camshaft free combustion engine, a pressure fluid, such as a liquid or a gas, is used to achieve a displacement/opening of one or more engine valves. This means that the camshafts, and related equipment, that conventional combustion engines use to open engine valves to let air in and let exhaust fumes out, have been replaced by a less volume-demanding and more controllable system. However, it shall be pointed out that the present invention may also be used in a combustion engine comprising conventional cam shafts.
The combustion engine comprises conventionally a strong valve spring in the shape of a coil spring adapted to return the respective engine valve to a closed position of the combustion chamber. When designing these coil springs, several factors need to be weighed to obtain an adequate closing at different engine speeds and to ensure that the engine valve does not unintentionally open at the wrong occasion. In reality, the coil spring must be designed for the most extreme situations, which in most operational conditions entail that the valve spring force is unnecessary large, which in turn entail unnecessary power consumption. Thereto, the spring force of a traditional valve spring has a linear increase.
Pneumatic valve springs are, for instance, known from Formula 1 engines, in which conventional metal coil springs are not fast enough for the extremely high engine speeds used. These solutions includes an oxygen free gas as a gas spring and are thereto expensive and require complicated sealing for preventing the gas from leaking out or air/oil from leaking in. From a cost perspective, it is not justifiable to use the technique used in Formula 1 engines in a combustion engine for a passenger car or a heavy vehicle.
In combustion engines according to the present invention, pneumatics as well as hydraulics are used for its operation, and in these systems it is desirable that the hydraulic fluid is present in the gas that usually is constituted by air, for lubricating, cooling, and sealing purposes. The term hydraulic in this disclosure is meant to mean engine oil if nothing contrary is stated.